1. Technical Field
The present invention relates to a projection system suitable to be incorporated in a projector that enlarges and projects an image formed on an image display device and a projection-type image display apparatus that incorporates the projection system.
2. Related Art
In recent years, in a high-luminance (at least 10,000 lumens (lm), for example), high-resolution projector, it is desired to perform wide-field-angle image projection. JP-A-2010-152277 and JP-A-2011-107200 each disclose a projection system capable of achieving high luminance and high resolution. The projection system described in JP-A-2010-152277 is formed of first to sixth groups in each of which each lens is a single lens, and the magnification is changed by movement of the second to fifth groups with the first and sixth groups fixed. The projection system described in JP-A-2011-107200 is formed of first to sixth groups in each of which each lens is a single lens, and the magnification is changed by movement of the first to fifth groups with the sixth group fixed.
However, the projection system described in JP-A-2010-152277 provides a half field angle of 28° at the wide angle end, and the projection system described in JP-A-2011-107200 provides a half field angle of 28.2° at the wide-angle end. Each of the projection systems, each of which provides a half field angle smaller than 30°, is not a wide-field-angle projection system. Each of the projection systems is therefore insufficient in an application for a large screen in some cases because the distance between the projector and a screen is short.